The weather gods were petulant the past couple of days. They had set up a swirling mass of wetness off the Delaware/New Jersey coast and left it there to cause headaches among weather forecasters in the DC area. I set up the telescope anyway, despite the rain that fell in the morning and the pervasive clouds since. Astro-geeks are silly in that way. I killed the cloudy time with a trip to Home Depot and worked on installing a new range cooktop in the kitchen. The telescope mount was happily tracking nothing in particular. At least it wasn't raining.

Venus and Mercury were due to appear to pass very close to each other today. They are far apart in terms of real distance in their orbits around the Sun, but the projection on the plane of the sky as seen by us here on Earth is such that, at their closest about noon EDT today, they were a very miniscule 3.9 arcminutes apart. It was cloudy at noon, so by the time I got a glimpse they were a bit further apart. The chart at left shows Venus and Mercury at two-hour spacings today. Times are Eastern Daylight Time, and the chart dimensions are in the lower right corner. The line joining Venus and Mercury at noon EDT marks their closest approach, 3 arcminutes and 53 arcseconds. (I used SkyTools to make this chart. SkyTools is a fabulous tool for planning an observing session, among the many useful things that it does.)

Around 12:30pm or so the clouds thinned enough to allow putting the finder scope crosshairs on the Sun. This took about half an hour, of maddeningly occasional 1 to 10 second glimpses, to accomplish. The image at left shows the setup I used for this. Baader solar film (in homemade holders) is in front of both the refractor and the finder objective lenses. By this time the Sun had crossed the meridian, and the mount was complaining that it really, really wanted me to flip the telescope to the other side of the polar axis. I was very glad to finally be able to push the "align" button on the GOTO control paddle. Now I wondered how well the finder scope was aligned with the optical axis of the telescope. It's usually surprisingly repeatable despite unattaching and reattaching to the telescope, but old man Murphy tends to make unwelcome appearances at times like this. I started the video camera feed to the laptop, making sure that was working properly. Slewed eastward to the supposed position of Venus.

And waited.

This being the daytime, with Polaris thus a bit hard to find, the next vexing issue was how poorly I'd estimated where Polaris is for the telescope mount polar axis alignment. At this spot in the driveway, it's roughly mid way between a neighbor's tree and their TV antenna. Too late now. I used the time to experiment with the filtering required to cull all those photons before blasting the CCD. It turns out a 30-Angstrom (FWHM) narrow band filter was just about right, or so I guessed from having nothing to image but bright cloud bottoms.

Finally, just before 2pm, a sucker hole passed by. Here we go, this is it. I removed the video camera and a spacer tube and put in a diagonal and 22 mm eyepiece: voila! There was Venus, smack in the center of the FOV, with little Mercury plain as day very nearby. The alignment gods were smiling. I suppose I didn't need to spend precious seconds with the eyepiece check, but I'm glad I did — there's still no substitute for seeing such a wondrous thing with your own eyes. I gawked for a bit longer. I will always remember the image.

With time ticking and the hole in the clouds passing, I then pulled the diagonal and eyepiece, put the spacer and video camera back in, and used up more time focusing.

Oh my: focusing. I hadn't ever used this configuration before (narrow band filter that I usually use for solar imaging, but without the Herschel wedge or neutral density filters or barlow lenses). Thus, I didn't have any Sharpie lines drawn on the focus tube to preset the focus. If you've ever had no idea where the magical in-focus position is with only the small field of view of a video camera to go by, you'll know what a disaster this could've been.

Fortunately, the focus gods were smiling at whatever the alignment gods were smiling at (perhaps the antics of the weather gods), and my seat-of-the-pants guess of distances turned out to be fairly close. So focusing took only an amazingly small number of seconds. Good thing: the end of the sucker hole was fast approaching, making me nervous. Nervous is never good where things hardware-techie are concerned. Nervous people forget things. Cloudlets within the hole came and went a couple more times. Was I really in focus? There was no more time for futzing. I finally had to click the record button and hope that (1) I'd gotten things close enough and that (2) I'd not forgotten anything crucial. Wonder of wonders, I managed to coax a bit over a minute of proof onto the hard drive! (You thought I was exaggerating about the imminent end of that sucker hole?)

Here is a typical image frame. (Click on the thumbnail image to bring up a larger image.) A flat field calibration and a noise suppression algorithm have been applied, but the brightness and contrast have not been changed. The image scale is 1.68 arcseconds per pixel, so this image is about 18×13 arcminutes. Note the structure in the blobs of moisture (i.e., clouds), even at this small scale, as well as the bright (daylight!) sky background. (Remember that this is through a filter with a very narrow bandpass.) Venus is shining at magnitude -3.9, while little Mercury, just 4.1 arcminutes southwest of Venus, is a little over 30 times fainter at magnitude -0.1. The next time Mercury and Venus will appear less than 10 arcminutes apart in the sky will be the morning of October 7, 2030, when they will pass within 5.3 arcminutes of each other.

A lot more fun is to view a movie (3.8 MB) I clipped and cropped from the longer raw AVI. The movie zooms by at twice real-time rate due to the fact that I recorded the AVI file at 5 frames per second while the MPEG format minimum is 10 fps. None of the alternative formats or AVI compression schemes I tried yielded a smaller file size without inflicting hopelessly bad video quality. As it is, the MPEG linked above is barely tolerable. Welcome to the hideous world of video formats. You'll also notice a flat-fielding flaw just below Venus at times (there was a dust speck shadow, about four times the apparent diameter of Venus's disk, at that location in the raw frames). I'll have to fix that later. Finally, I think the apparent jerks in the time stream are due to the laptop hard drive struggling to keep up, even at just 5 fps. (Time warps would be a more exciting explanation, but I suspect the reality is considerably more mundane than that.)

About half an hour later another small hole in the clouds passed by, and I got another (even shorter) clip. Below I compare images from the second clip to those from the first clip to show the relative apparent motion of the two planets during the short time between the two clips. Within a couple of minutes (really: less than two!) of recording the second clip it suddenly rained and I had to quickly pull everything inside. Wetness, wetness, everywhere. (But not on any lenses — I'm not that reckless.) Time to go and finish installing the new cooktop.

Here is an image composed of (1) a stack of frames extracted from about 54 relatively cloud-free seconds of the first AVI file, centered on 1:52pm; and (2) a stack of about 3 seconds of frames from the clearest section of the second AVI, centered on 2:31pm. I've stretched the pixel intensity histogram so as to lower the sky background to approximate darkness. Venus is clearly overexposed. Needless to say, atmospheric seeing was very poor due to two cloud decks streaming in opposite directions overhead and to the humid air near the ground roiling from the recent sudden influx of sunlight (and heat) locally. I placed Venus from each original stacked image in the same location for this double exposure, and I made sure the position angles of Mercury with respect to Venus were correct in each original image before combining. As you can see, the motion of Mercury relative to Venus is very noticeable, even over a span of just 40 minutes. The distance between the two positions of Mercury (relative to Venus) is 26 arcseconds.

Later, around 4:30pm, I looked up to see large patches of blue, and sunlight streaming all around. I thought about hauling everything back out, reconsidered, then thought about getting mad at the Fates. But I had experienced already some truly magical moments, the glow from which I was still enjoying, so I went back to the kitchen. Sure enough, after about the time it would've taken to almost — but not quite — get set up and aligned again, the clouds came back and covered the sky. The gods had smiled enough for one day. I was fine with that.